Final answer:
Physics concepts are applied to determine the amount of water condensing out of air when it cools. Specifically in this scenario, a numerical answer requires the saturation vapor densities at the given temperatures and relative humidity. Without such data, the answer focuses on the process and factors influencing condensation.
Step-by-step explanation:
To answer the student's question on how many grams of water must condense out of each cubic meter of air if the temperature falls from 25.0°C to 15.0°C with a relative humidity of 90.0%, one needs to understand the concept of relative humidity and the relationship between temperature and the air's capacity to hold water vapor.
The amount of water vapor the air can hold depends on the temperature; warmer air can hold more water vapor than cooler air. When the air cools down, it can reach a point where it cannot hold all of its moisture, resulting in condensation. This point is known as the dew point.
Using the provided information, we can determine the saturation vapor densities at both temperatures using psychrometric charts or relevant data tables. Assuming we have those values, we would calculate the difference in the maximum amount of water air can hold at 25.0°C and at 15.0°C. Multiplying this difference by the initial relative humidity gives us the amount of water that condenses out per cubic meter.
Unfortunately, without explicit values from such a chart or table, we cannot provide a numerical answer. However, it is important to understand that the precise quantity depends on the specific saturation vapor densities at the given temperatures.